Many communications related tasks and applications, which have conventionally been dealt with by mail, telephone or personal contact, have been evolved into a web-based form in which communications is effected using the internet. One reason for this evolution is that the internet can provide a facility for communicating information more efficiently and quickly than conventional forms of communication. However, one disadvantage of the internet concerns security and privacy, since data communicated via the internet can be intercepted, altered and/or divulged to other parties.
For certain applications, it is necessary for a number of users to submit documents to a recipient data processing apparatus. For example users may be required to submit the documents to the recipient data processing apparatus, where the recipient apparatus is only able to operate on the received data after a predetermined event, such as the expiration of a time limit. Under these circumstances privacy, authentication and security of each submitted and received document should be maintained from the point of submission of the document until, and potentially after, the time limit has expired. For document distribution and authentication, concerned parties require assurance that a document communicated via the internet has not been tampered with, either to alter the document in some way or to determine the content of the document.
One example where secure document distribution and authentication is required is contract tendering, another example being a closed bidding process in which sealed bids are communicated to a vendor. For the closed bidding process the vendor is able to open the sealed bids and select the most appropriate bid, after all bids have been received.
For the example of a tendering process, tenders for a contract are submitted in a sealed form, which are deposited in a closed tender box until a date has passed. After the appropriate date, the tenders are opened and revealed to an administrator of the contract. The most appropriate bid may then be selected, with assurance that the bids are competitive, in the sense that there has been no collusion between the bidding parties. However, to ensure that competition has been maintained and the contract has been awarded on a fair basis, both the bidding parties and the contract administrator require assurance that the bids or tenders cannot be opened and/or modified by a competitor, otherwise a competitor may gain an unfair advantage. On the other hand the tendering parties want assurance that bids or offers submitted have not been opened by anyone without authorisation, especially before a due date and time.                One possible remedy for the disadvantages associated with communication vis the internet is to encrypt data. Previously proposed e-transaction security procedures include two methods, which are frequently combined:        (i) users use digital id's to prove their identity (akin to a signature), and        (ii) data is encrypted using some form of Public Key Infrastructure (PKI) where a combination of public/private keys ensures that only those who have the private key have the authorisation to decrypt encrypted data.However, if encryption fails, encryption does not generally provide any indication that an abuse has occurred. A corrupt user with all the relevant authorisations may use the encryption key to access bids or tenders before a due date/time, thereby being able to favour one competitor over another. Similarly, a tendering party or bidder with all the relevant authorisations may use the encryption key to access and modify its own data after a time/date that the bids/offers have been time locked and frozen. Furthermore a hacker, whether interested in the tender or otherwise, could hack into the server and manipulate data        
It would be desirable to provide a system, which can utilise data communications networks such as, for example, the internet, for document distribution, which provides improved assurance of authentication and security of the distributed documents.